The department has used two unmanned aircraft systems, or drones, as a law enforcement tool since June. The drones, which cost $17,500, have assisted the department in a house explosion and a car crash. They can also pick up and drop off lightweight items.

Madison is one of a growing number of police agencies that have purchased drones for public safety efforts, the Wisconsin State Journal reported .

A 2017 report by the Bard College Center for the Study of the Drone found that around 347 state, local and county police, fire and emergency departments have purchased a drone in the United States. Wisconsin accounts for 18 of those agencies.

The American Civil Liberties Union has raised concerns about invading privacy, including whether drones could use facial recognition technology or microphones to track movements and record private conversations.

Lt. Mike Hanson is commander of the department’s drone team. Hanson said that Wisconsin police must obtain a warrant before using a drone to gather evidence where someone may have a reasonable expectation of privacy.

Hanson said drones will not be used to hover in private yards or near homes to try to catch someone violating the law.

He said the team is figuring out best practices for the drones, but that feedback from the public and lawmakers has been positive.

“For us it’s been a year of learning, training, testing,” Hanson said. “We know that we like this program. We want to see it grow over the years.”